Amperometric determination of optically active 1-phenylethanol using chiral nitroxyl radical-modified polypyrrole films prepared by electrochemical polymerization

Polymeric chiral nitroxyl radical catalysts were prepared on an electrode surface by electrochemical polymerization of (6S, 7R, 10R)-2,2,7-trimethyl-10- isopropyl-1-azaspiro[5.5]undecane-1-yloxyl precursors containing a pyrrole side chain. This modified electrode gave a reversible electron transfer for the nitroxyl radical/oxoammonium ion redox couple in cyclic voltammetry at +0.72 V vs. Ag|AgCl. The modified electrode was used for electrocatalytic oxidation of (R)-(+)- and (S)-(-)-1-phenylethanol as an optically active sec-alcohol. Cyclic voltammetric studies showed that the catalytic current for the oxidation of (S)-(-)-1-phenylethanol is greatly enhanced as compared with a small enhancement in the oxidation current for the (R)-isomer. The (S)-isomer can be detected selectively in a mixture of (R)-(+)- and (S)-(-)-1-phenylethanol, even in the presence of an excess amount of (R)-isomer.